Manchester United manager Sir Alex Ferguson has called Manchester City's conduct in sacking manager Mark Hughes 'unacceptable'.
Hughes was axed earlier this week despite the Citizens having lost just twice in the Premier League this season, with Roberto Mancini having been drafted in as the Welshman's replacement.
It later emerged that City had held talks with Mancini several weeks before making the change following a 4-3 home win over Sunderland last Saturday.
Ferguson told reporters:"It was unacceptable behaviour.
"It doesn't matter whether you have lost 20 games or two, there is a way to treat people.
"For some reason Christmas seems to bring out the worst in directors. I do not know how you can do something like that.
"From Saturday morning the rumour mill was working and Mark must have realised it was his last game. It was a terrible position to be in."